There are several known methods for preparing aromatic methylenedioxy products including the methylenation of the corresponding ortho-dihydroxy precursors. However, all of the known processes suffer from one or more of the following disadvantages:
(a) They employ costly methylenation agents such as bromine and iodine derivatives; PA1 (b) Dilute aqueous solutions are required to assure intramolecural cyclization and preclude the intermolecular reaction which generally results in the formation of dimers and polymers. And, when the aqueous solutions are too dilute there is the problem of low yield and the separation of the mother liquors and recovery of same, and these additional steps make the process uneconomical; PA1 (c) Dipolar aprotic solvents such as dimethylsulphoxide and dimethylformamide under anhydrous donditions are employed; and although these solvents afford good yields of the dioxymethylene product and good reaction speeds are obtained, the consumption and recovery of costly solvents renders the process uneconomical.
We have now discovered a new method for the preparation of methylenedioxybenzene products which overcomes the aforementioned difficulties